Molecular Genetics (Unit 3) - chapter 6 Flashcards by Diya Vyas

Recall _______ experiments with pea plants
in the 1800’s

Mendel’s

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He proposed a “factor” for each trait that was
passed on from parents to offspring – ______

genes

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A ____ is the coding region of DNA that
contains instructions to build a protein

gene

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Some fundamental genes are shared by almost
all living organisms (T/F)

TRUE

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There is a lot of _____ that needs to fit inside every
single cell of an organism

DNA

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This is accomplished same or differently in prokaryotes and eukaryotes

differently

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In eukaryotes, DNA coils around ______ proteins
to form complexes that combine to form
______

histone
chromatin

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Eukaryotes also have small amounts of DNA in
their _______ and _______, which is
similar in structure to that found in prokaryotes

mitochondria and chloroplasts

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DNA in archaea and bacteria is found in
simple _____________

loop-shaped chromosomes

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The _______ consists of the entire set of DNA in
an organism

genome

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They may also contain ______, small
accessory loops of DNA

plasmids

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Bacterial DNA is found in an area called the _______

nucleoid

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Humans and many other eukaryotes are _____ –
their chromosomes occur in homologous pairs

diploid

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Bees, wasps, and ants are _______: the
females are diploid, while the males are haploid

haplo-diploid

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Plants can be _____ …

haploid, diploid, triploid, tetraploid,
hexaploid…

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In 1868, he studied
the composition of the
nucleus

Meischer

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Meischer Extracted an unknown substance
that was _____ and contained ______

Named it “_____”

acidic, phosphorus
nuclein

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Meischer Collected ____ from
bandages (mostly
WBC’s)

pus

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In 1928, he studied pneumonia bacteria
(epidemic in Europe at the end of WWI)

Griffith

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___-strain (smooth) vs.
___-strain (rough)

S-strain (smooth) vs.
R-strain (rough)

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Griffith research Showed some sort of
hereditary transmission - _______

transformation

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Griffith Injected ____ with each
strain and various
combinations

mice

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Based on Griffith’s
findings, they carried
out similar studies in
1944 using
Streptococcus

Avery, McLeod,
&McCarty

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Possible transforming
substances were ___, ____ and _____

DNA, RNA, and proteins

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Results showed that ____ was the hereditary substance (went against current thinking – proteins)

DNA

In 1952, they attempted to verify if DNA or protein was the genetic material

Hershey & Chase

Used _______ and E. coli bacteria

bacteriophages

Labelled _______ of phosphorus (DNA) and sulfur (protein) to determine what part was being affected (DNA or protein coat)

radioisotopes

Found radioactivity only inside cells : _____

DNA

An organic chemist Disagreed with common thinking that there was an equal concentration of A, T, C, and G

Chargaff

In 1950, he discovered that the bases occur in definite ratios where A= ___ and C = ____ Now known as Chargaff’s Ratios

A= T and C = G

Purine example

A and G

Pyrimidines example

T and C

Used X-ray crystallography to study shape of DNA molecule

Wilkins & Franklin

____ produced clearer crystallographs than Wilkins, whose work showed a ____ structure

Franklin helical

X shape suggested _______ rotating ______, with _______ backbone on the outside

double helix clockwise sugar-phosphate

In 1952, they were building a variety of models of DNA to determine the structure

Watson & Crick

Wilkins revealed some of Franklin’s work, which helped them realize that a double helix model fit all of the known information Strands must run _______

anti-parallel

Due to the work of ______ (4 ppl), an accurate model of DNA was determined in the 1950s

Watson, Crick, Franklin, and Wilkins

DNA has a _____helix structure, with the “sides” consisting of alternating _______ and ________

double deoxyribose sugars phosphates

The “rungs” consist of ______ base pairs (A, T, C, &G)

nucleotide

The strands run _________ to each other

antiparallel

The _____ on the 3’ carbon of deoxyribose is at one end of the strand

hydroxyl

The ________ on the 5’ carbon is at the other end

phosphate

The strands run in _______ directions

opposite

In 1958, Meselson and Stahl verified that DNA replication was _________

semiconservative

Then transferred colonies to a growth medium of _______, allowed to _____ for one or two rounds

normal N replicate

Used “heavy” _____of nitrogen (15N) to label E. coli bacteria (lots of N in DNA!)

isotopes

:. New DNA would contain “light” N and ______ could be measured

density

Eukaryotic DNA replication is similar to prokaryotic, but more complex due to its ________ and ________

linear configuration sheer volume

DNA helicase Unwinds DNA by breaking apart _______ between base pairs

H-bonds

DNA replication Consists of 3 steps:

Strand separation Building complementary strands Dealing with errors

_______: Y-shaped region of separation

Replication fork

Step 1: Strand Separation - ________ binds to specific nucleotide sequences (replication origins)

DNA helicase

2 problems:

Tension on DNA behind fork (topoisomerase) Separated strands tend to anneal (SSBPs)

Helicase will separate strands in both directions, forming a __________

replication bubble

There can be many replication bubbles at any given time on a strand of DNA (T/F)

TRUE

The replication bubble will extend until _______

they meet and merge

Step 2: Building Complementary Strands - _________ are enzymes that add nucleotides to build new DNA strands

DNA polymerases

It takes about ______ to replicate the entire genome

an hour

DNA is replicated at a rate of ______ per second at each fork

~50bp

_______ are added to the 3’ end of the existing “template” strand, which is read in the 3’ to 5’ direction

Nucleotides

New strand: ___🡪 ___

5`🡪3`

DNA polymerases need ____, which comes from the hydrolysis of 2 Pi from a _________ as it is added to the strand

energy nucleoside triphosphate

strands are synthesized ___ to ____

5’ to 3’

Nucleotide = ______ + _____ + ______

Sugar + Base + Phosphate

DNA polymerase III can only add to the ___ end of a strand, so ________ builds a short (10 – 60 bp) complementary RNA sequence called an ______

3’ RNA primase RNA primer

Nucleoside = _____ + _____

Sugar + Base

One strand will be able to be synthesized continuously: ________

leading strand

_______ begins adding to the primer in the 5’ to 3’ direction

DNA polymerase III

The other side must be made in smaller fragments, using multiple RNA primers: ________

lagging strand

These DNA fragments on the lagging strand are called _______ fragments

Okazaki

_______ long in eukaryotes _______ long in prokaryotes

100-200 bp 1000-2000 bp

_________ removes the RNA nucleotides and replaces them with those of DNA

DNA polymerase I

As each fragment extends, it will run into the _________ of the previous Okazaki fragment

RNA primer

________ catalyzes the formation of a phosphodiester bond between the nucleotides of the two fragments

DNA ligase

Step 3: Error Correction - DNA polymerases also __________ the newly synthesized strands

proofreads and corrects

For example, if there is a base pair mismatch (e.g. A and C), ________ can’t continue

DNA polymerase III

It will back up, replace the ______, and continue

nucleotide

Sometimes, errors will be missed (1 in every million bp) which __________

distort the shape of DNA

_________ has a repair mechanism that can determine which is the original correct template strand, and remove the incorrect bases so they can be replaced

DNA polymerase II

Eukaryotic DNA Organization: Negatively charged DNA is wrapped around positively charged _______ proteins

histone

8 Histone proteins combine to form a __________ which helps to wrap DNA

Nucleosome

Nucleosomes are further condensed to form __________ (6 nucleosomes)

solenoids

Solenoids (also called chromatin fibres) are further coiled and folded until they form __________

chromosomes

DNA replication results in small amounts of _____ DNA after each replication

lost

Prokaryotic DNA Organization: Commonly only ____ chromosome that can be circular

one

nuclear membrane or not? (in Prokaryotic DNA Organization)

Smaller pieces of DNA float throughout the cell and are called ______

Plasmids

can Plasmids be shared between bacteria

YES

a repeating sequence of DNA at the end of a chromosome. Protects coding regions from being lost during replication.

Telomere

twisting of prokaryotic DNA to reduce the volume

Supercoiling

Telomeres help prevent the loss of ________

important parts of DNA

Telomeres during Replication: Telomeres ______ after each division

shorten

The Several Functions of Telomeres: Help to prevent chromosome ends from ______________ Prevent DNA degradation from _________ Assist ___________ in distinguishing DNA breaks from chromosomal ends Determine how many times a cell can _______

Help to prevent chromosome ends from fusing to other chromosomes Prevent DNA degradation from other enzymes Assist DNA repair mechanisms in distinguishing DNA breaks from chromosomal ends Determine how many times a cell can divide

Cells can only divide so many times before they lose their ______ and important DNA starts to become ___

telomeres lost

Human cells can divide around ___ times before telomeres become too short

the total number of times a cell can divide

Hayflick Limit

______ must continue to divide and produce more of them

Sex cells

adds more DNA to the shortening telomeres of sex cells so they can continue to divide

Telomerase

______ and some White Blood Cells also use Telomerase

Stem Cells

As we age more and more of our cells reach the ________ and begin to die off

Hayflick limit

Cancer cells can continue to ________ because they produce large amounts of _______ and continue to repair their telomeres

divide indefinitely Telomerase

Molecular Genetics (Unit 3) - chapter 6 Flashcards

(103 cards)